I've uninstalled both the recent updates with no successs. I also tested my memory for errors using memtest86+, and the memory passed all tests after an hour. (3gb is a lot of memory to test...)

Here is the error message I receive every 30 seconds after connecting:

Problem signature:
Problem Event Name: APPCRASH
Application Name: mirc.exe
Application Version: 6.21.0.0
Application Timestamp: 4565c21f
Fault Module Name: ntdll.dll
Fault Module Version: 6.0.6000.16386
Fault Module Timestamp: 4549bdf8
Exception Code: c0000005
Exception Offset: 0006089e
OS Version: 6.0.6000.2.0.0.256.4
Locale ID: 1033
Additional Information 1: 74e7
Additional Information 2: beea8309ec58a0464c96405b75577c80
Additional Information 3: 79f5
Additional Information 4: 58fd9e46ef49b5eb4e29e4b0a859e72c

Is there anything I can do short of wiping Vista and going back to x64?